**5.1 Humic acids**

*Urban Horticulture - Necessity of the Future*

temperatures below 50°C [16].

treatment used.

pathogens [16].

infections [21].

use of products.

radiation, hydrolysis in strongly acidic or basic media, chemicals that affect pathogens, competition with other microorganisms, time, etc. (World Health Organization, 2018) [16]. If handled properly, composting can reduce pathogen levels [17]. In the inactivation of nonpathogenic *Escherichia coli*, pathogenic *E. coli* O157:H7, and *Salmonella* spp., several types of waste, such as animal manure and sewage sludge, have been reported during composting [18]. However, the persistence of *Listeria* spp., *Salmonella* spp., and nonpathogenic *E. coli* during composting [19] and the survival of *Salmonella* spp. and nonpathogenic *E. coli* in mature composts [20]. Most research on *E. coli* and *Salmonella* spp. have focused on manure or sewage sludge, but little attention

With regard to temperature, in many small composting units, degradation activity is limited by low temperature, well below 55°C. This is a very serious limitation when it comes to disinfection, since for many pathogens there is little or no reduction to

According to the US Environmental Protection Agency (US EPA) standard, Class A compost should not exceed the maximum *Salmonella* spp. limits (less than 3 most likely numbers [NMP]/4 g) or thermotolerant coliforms (less than 1000 NMP/g). The final amounts of bacteria, biological and viral, depend on the type of

The current trend adopted in this field is to establish rigid rules that control the production process as well as to establish transport, packaging, and storage standards rather than setting pathogen limits on final products. For example, to acquire the characteristics necessary to be used in agriculture, sludge must undergo an additional disinfection process that ensures the reduction of the density of

With regard to the risks of pathogens in organic fertilizers, it can be said that hazards can be excluded when production is industrialized, and this includes several disinfection procedures (pasteurization, drying, chemical media, etc.). In addition, more or less stabilized organic substances, if poorly preserved and stored, can serve as excellent substrates for pathogens and become carriers of

In the use of organic fertilizers, it is necessary to apply the precautionary principle, with the adoption of protective measures if there are suspicions that the products present a risk to public health or the environment. On the other hand, the danger of organic fertilizers and their amendments is certainly related to the end

Many organic compounds persist for long periods in soil, subsoil, aquifers, surface water, and aquatic sediments. These compounds, which can be of low or high molecular weight and that resist biodegradation, are known as recalcitrant.

Composting has been widely used for the remediation of organic pollutants as it, with adequate aeration, water, C-to-N ratio, and duration, accelerates their destruction [23]. The degradation of pesticides during composting depends on the pesticide and the substrate on which it is co-composted [24]. Strom [25] reported on the breakdown of organophosphorous pesticides and carbamates during composting. However, organochlorinated insecticides are resistant to degradation (Buyuksonmez et al., 1999). Differences in degradation may be related to inherent differences in the biological metabolism of the compound but may also be related to the composting process. Short-term composting (<60 days), which consists largely of the thermophilic phase, without adequate curing (mesophilic phase), may not be

Many pesticides, mainly herbicides, have this characteristic [22].

sufficient for the degradation of pesticides [26].

has been paid to other substrates, such as green waste.

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Humic substances (HS) are the last substances resulting from chemical, biological, and physical transformations of plant and animal matter. The main compounds resulting from this transformation are humic acids, fulvic acids, and humines. Within these substances, humic acids, compounds soluble in alkaline solution and insoluble in acid solution and having a higher molecular weight, are the most important components [27, 28]. These substances, for their characteristics and effects on plants, have been considered as biostimulants [29].

HS are mineral compounds, among them essential elements for plants, mainly carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus (P), iron, copper, zinc and boron, in addition to functional groups among which stand out aromatic, aliphatic, carboxylic, and phenolic compounds (from [30–32]). HS are composed of hydrophobic fractions composed of aliphatic and aromatic compounds, while in another fraction, hydrophilic is composed of irregular humic fractions. These compounds, for their physicochemical characteristics, cause various effects on plants.

Among the metabolic processes that contribute to promote the growth and development of plants is the stimulation of the activity of key enzymes for the absorption and distribution of nutrients [33, 34]. The interaction of humic substances with proteins and lipids of the cell membrane improves the absorption of nutrition [35]. Mora et al. [36] mention that the presence of AH stimulated the activation of the H+-ATPase pump which led to a better distribution of NO3 <sup>−</sup> from the root to the leaves. HSs can form latent complexes with metal ions, contributing to increased availability for root absorption as well as improving the distribution, within the plant, of metal ions [37].

There are various materials from which HS is obtained, which have been used in different crops in the hydroponic system. These substances have shown significant effects on these plants, improving growth and nutritional condition, mainly.

Haghighi and Teixeira [38] added 25 mg L<sup>−</sup><sup>1</sup> and 50 mg L<sup>−</sup><sup>1</sup> of HS extracted from forest soil moistified monthly to the nutrient solution used in the cultivation of tomato grown in perlite/vermiculite substrate. These HS were composed of 0.57% nitrogen, 0.03% phosphorus, and 4.5% potassium, with a pH of 4.5. Basically the addition of 50 mg L<sup>−</sup><sup>1</sup> of HS was the treatment that provoked the greatest effect in plants, increasing by 19% yield, 29% protein, 436% photosynthesis in growth stage, and 34% in fruiting stage. Other variables such as nitrate content, sugar content, and acidity in addition to antioxidant enzymes and chlorophyll were not affected by the presence of HS. These authors attributed the null effect on the abovementioned variables to the low concentrations of HS evaluated in the experiment.

Jannin et al. (2012) used 100 mg L<sup>−</sup><sup>1</sup> HS extracted from black peat for the formulation of Hoagland and Arnon nutrient solution (1950), for the cultivation of canola in floating root system. This material contained mainly 125, 40, 14, 9, and 2 mmol L<sup>−</sup><sup>1</sup> of potassium, sulfur, calcium (Ca), iron, and phosphorus, respectively, in addition to very low amounts of cytokinins such as zeatin, isopentenyladenine, and isopentenyladenosine. The plants were evaluated at days 1, 3, and 30 after the start of treatment, wherein the most significant effects were found at 30 days. The dry root weight was increased by 88%, while the total dry weight of the plant was

increased by 29%. Nutrient absorption was increased with the presence of HS by 79% sulfur, 75% copper, 66% magnesium (Mg), 60% calcium, 57% nitrogen, and 47% potassium. Similarly, root nitrogen increased by 108% and sulfur increased by 76% in the leaf and 137% in the root. The abovementioned increases were the result of the expression of transporters present at the root responsible for the absorption of nitrogen and sulfur, in addition to the activity of the enzyme nitrate reductase.

The results showed that overall all materials were superior to the control. In particular 1 mg C L<sup>−</sup><sup>1</sup> increased the root length by 65% and the foliar area by 54%. The activity of the enzymes glutamine synthetase and glutamate synthetase, essential in nitrogen metabolism, were increased by 29% and 12%, respectively, with the addition of 10 mg C L<sup>−</sup><sup>1</sup> . Some important compounds in metabolism were increased. Protein content was increased by 43% in leaf and 8% in root at the concentration of 10 mg C L<sup>−</sup><sup>1</sup> and 1 mg C L<sup>−</sup><sup>1</sup> , respectively, while the foliar concentration of glucose and fructose were increased by 10% and 25% with the presence of 0.5 mg C L<sup>−</sup><sup>1</sup> . The activity of the enzyme phenylalanine ammonium lyase, participant in the production process of phenolic compounds, was increased by 51% by the presence of 1 mg C L<sup>−</sup><sup>1</sup> , so the content of phenolic compounds was increased by 15%.

#### **5.2 Microorganisms and phytohormones**

The use of nutritious solutions cast from organic fertilizers, such as composts, lombricomposts, vermicomposts, etc., may constitute an economic and environmental alternative to the use of chemical fertilizers for food production [39].

Organic fertilizers differ in quality, stability, and maturity because they depend on the organic waste and method by which they are prepared, so their chemical and biological composition varies and thus the nutritional composition and other elements that are present in the solutions obtained from them [40].

It is well documented that organic fertilizers contain soluble mineral nutrients such as nitrogen, phosphorus, potassium, magnesium, calcium, and other microelements, in addition to humic and fulvic acids, which the plant uses for its nutrition [39, 41]. But there is also the presence of phytohormones such as auxins, gibberellins, and cytokinins that are indispensable for the growth and development of plants [42–44].

In plants, phytohormones auxins, gibberellins, and cytokinins are the most common. Auxins, usually in the form of indolactic acid (AIA), are responsible for stimulating cell division, apical growth, and root branching [45]. Gibberellins, mainly in the form of gibberellic acid, are involved in various developmental and physiological processes, including seed germination, seedling emergence, stem and leaf growth, flowering, senescence, maturation of the plant [46]. Cytokinins play a key role in the process of cell division and bud growth and maintain photosynthetic activity and stoma opening during drought [47]. Therefore the presence of these hormones in organic fertilizers and the solutions obtained from them are of great importance and have to be considered; however, their presence has been less documented because they are difficult to detect and quantify, since they are usually found in trace concentrations and/or because they are immersed in a complex biological matrix, which makes their analysis quite difficult [44], but there are still some reports.

Zandonadi and collaborators reported the presence of indole-3-acetic acid (auxin) in humic acid extracted from a vermicompost. Zhang and collaborators (2014) reported the presence of cytokinins in tea also from a vermicompost. A study by Plant and collaborators (2012) reported the presence of isopentenyladenine-cytokinin, gibberellin 4 (GA4), and gibberellin 34 (GA34) in extracts of thermophilic compost based on chicken manure, waste vermicompost of food, and vermicompost based on chicken manure and the presence of gibberellin 24 (GA24) in vermicompost tea based on chicken manure. They also reported that a higher

**85**

sustainably.

*Nutritive Solutions Formulated from Organic Fertilizers DOI: http://dx.doi.org/10.5772/intechopen.89955*

composting [50], for example, *Azospirillum* spp. [51].

genera *Proteus*, *Klebsiella*, *Escherichia*, *and Xanthomonas* [43].

**6. Trials of organic nutrient solutions in vegetables**

cal fertilizers. Solutions were varied in electrical conductivity:

5.Steiner solution with electrical conductivity of 1.5 dS m<sup>−</sup><sup>1</sup>

6.Steiner solution with electrical conductivity 2.0 dS m<sup>−</sup><sup>1</sup>

ganisms present in fertilizers.

concentration of phytohormones can be attributed to increased activity of microor-

These phytohormones are produced by microorganisms present in organic fertilizers that come from soil and plant waste with which they are prepared [48, 49]. These microorganisms that produce these and other plant growthpromoting compounds are also known as plant growth-promoting microorganisms (PGPM) and are largely also responsible for biodegradation of the substrate or organic waste in the process of the production of organic fertilizers, mainly in

Among the microorganisms that produce auxins are those belonging to the genera *Azospirillum* spp. [52], *Azotobacter* spp. [53], *Rhizobium* spp. [54], *Bacillus subtilis* [55], *Bradyrhizobium* spp. [56], *Enterobacter* spp. [57], and *Trichoderma* spp. [58], to name a few. Within the production of gibberellins, *Azospirillum* spp. [59], *Bacillus* spp. [60], *Rhizobium* spp. [61], *Aspergillus* spp. [62], *Gibberella* spp. [63], and *Penicillium* spp. [64] are reported. The production of cytokinins is well characterized in microorganisms belonging to various genera such as *Azospirillum* [65], *Bacillus* spp. [66], and *Pseudomonas* spp. (Grokinsky et al., 2016) as well as the

Although there is much research on the identification and quantification of phytohormones produced by various microorganisms (mainly bacteria and fungi that may be present in the organic waste and soil used for organic fertilizer processing and solutions obtained from them), studies related to the identification and quantification of phytohormones present in these are still scarce. This is due to the complexities necessary for the development of more sensitive and specific extractions, preparations and detection methods to analyze phytohormones. Quantification of phytohormones in organic waste solutions will be crucial for their complementation and supplementation with other compounds and improve food production more

**6.1 Commercial and nutraceutical quality of compost extract in tomato fruits**

We established a greenhouse trial with six treatments to determine the commercial and nutraceutical qualities and yield of tomato fruits (*Solanum lycopersicon*) fertilized with bovine compost and hen teas, and was treated with synthetic chemi-

1.Compost extract of poultry manure with electric conductivity of 1.5 dS m<sup>−</sup><sup>1</sup>

2.Compost extract of poultry manure with electric conductivity of 2.0 dS m<sup>−</sup><sup>1</sup>

3.Compost extract of bovine manure with electric conductivity of 1.5 dS m<sup>−</sup><sup>1</sup>

4.Compost extract of bovine manure with electric conductivity of 2.0 dS m<sup>−</sup><sup>1</sup>

Commercial materials were used as sources, which ensure the absence of pathogenic organisms. The cattle compost was the Organo Del brand (85% organic *Nutritive Solutions Formulated from Organic Fertilizers DOI: http://dx.doi.org/10.5772/intechopen.89955*

*Urban Horticulture - Necessity of the Future*

and 1 mg C L<sup>−</sup><sup>1</sup>

**5.2 Microorganisms and phytohormones**

ticular 1 mg C L<sup>−</sup><sup>1</sup>

tion of 10 mg C L<sup>−</sup><sup>1</sup>

10 mg C L<sup>−</sup><sup>1</sup>

of 1 mg C L<sup>−</sup><sup>1</sup>

increased by 29%. Nutrient absorption was increased with the presence of HS by 79% sulfur, 75% copper, 66% magnesium (Mg), 60% calcium, 57% nitrogen, and 47% potassium. Similarly, root nitrogen increased by 108% and sulfur increased by 76% in the leaf and 137% in the root. The abovementioned increases were the result of the expression of transporters present at the root responsible for the absorption of nitrogen and sulfur, in addition to the activity of the enzyme nitrate reductase. The results showed that overall all materials were superior to the control. In par-

activity of the enzymes glutamine synthetase and glutamate synthetase, essential in nitrogen metabolism, were increased by 29% and 12%, respectively, with the addi-

Protein content was increased by 43% in leaf and 8% in root at the concentration of

, so the content of phenolic compounds was increased by 15%.

The use of nutritious solutions cast from organic fertilizers, such as composts, lombricomposts, vermicomposts, etc., may constitute an economic and environmental alternative to the use of chemical fertilizers for food production [39].

Organic fertilizers differ in quality, stability, and maturity because they depend on the organic waste and method by which they are prepared, so their chemical and biological composition varies and thus the nutritional composition and other

It is well documented that organic fertilizers contain soluble mineral nutrients such as nitrogen, phosphorus, potassium, magnesium, calcium, and other microelements, in addition to humic and fulvic acids, which the plant uses for its nutrition [39, 41]. But there is also the presence of phytohormones such as auxins, gibberellins, and cytokinins that are indispensable for the growth and development of plants [42–44].

In plants, phytohormones auxins, gibberellins, and cytokinins are the most common. Auxins, usually in the form of indolactic acid (AIA), are responsible for stimulating cell division, apical growth, and root branching [45]. Gibberellins, mainly in the form of gibberellic acid, are involved in various developmental and physiological processes, including seed germination, seedling emergence, stem and leaf growth, flowering, senescence, maturation of the plant [46]. Cytokinins play a key role in the process of cell division and bud growth and maintain photosynthetic activity and stoma opening during drought [47]. Therefore the presence of these hormones in organic fertilizers and the solutions obtained from them are of great importance and have to be considered; however, their presence has been less documented because they are difficult to detect and quantify, since they are usually found in trace concentrations and/or because they are immersed in a complex biological matrix, which

elements that are present in the solutions obtained from them [40].

makes their analysis quite difficult [44], but there are still some reports.

Zandonadi and collaborators reported the presence of indole-3-acetic acid (auxin) in humic acid extracted from a vermicompost. Zhang and collaborators (2014) reported the presence of cytokinins in tea also from a vermicompost. A study by Plant and collaborators (2012) reported the presence of isopentenyladenine-cytokinin, gibberellin 4 (GA4), and gibberellin 34 (GA34) in extracts of thermophilic compost based on chicken manure, waste vermicompost of food, and vermicompost based on chicken manure and the presence of gibberellin 24 (GA24) in vermicompost tea based on chicken manure. They also reported that a higher

and fructose were increased by 10% and 25% with the presence of 0.5 mg C L<sup>−</sup><sup>1</sup>

The activity of the enzyme phenylalanine ammonium lyase, participant in the production process of phenolic compounds, was increased by 51% by the presence

increased the root length by 65% and the foliar area by 54%. The

. Some important compounds in metabolism were increased.

, respectively, while the foliar concentration of glucose

.

**84**

concentration of phytohormones can be attributed to increased activity of microorganisms present in fertilizers.

These phytohormones are produced by microorganisms present in organic fertilizers that come from soil and plant waste with which they are prepared [48, 49]. These microorganisms that produce these and other plant growthpromoting compounds are also known as plant growth-promoting microorganisms (PGPM) and are largely also responsible for biodegradation of the substrate or organic waste in the process of the production of organic fertilizers, mainly in composting [50], for example, *Azospirillum* spp. [51].

Among the microorganisms that produce auxins are those belonging to the genera *Azospirillum* spp. [52], *Azotobacter* spp. [53], *Rhizobium* spp. [54], *Bacillus subtilis* [55], *Bradyrhizobium* spp. [56], *Enterobacter* spp. [57], and *Trichoderma* spp. [58], to name a few. Within the production of gibberellins, *Azospirillum* spp. [59], *Bacillus* spp. [60], *Rhizobium* spp. [61], *Aspergillus* spp. [62], *Gibberella* spp. [63], and *Penicillium* spp. [64] are reported. The production of cytokinins is well characterized in microorganisms belonging to various genera such as *Azospirillum* [65], *Bacillus* spp. [66], and *Pseudomonas* spp. (Grokinsky et al., 2016) as well as the genera *Proteus*, *Klebsiella*, *Escherichia*, *and Xanthomonas* [43].

Although there is much research on the identification and quantification of phytohormones produced by various microorganisms (mainly bacteria and fungi that may be present in the organic waste and soil used for organic fertilizer processing and solutions obtained from them), studies related to the identification and quantification of phytohormones present in these are still scarce. This is due to the complexities necessary for the development of more sensitive and specific extractions, preparations and detection methods to analyze phytohormones. Quantification of phytohormones in organic waste solutions will be crucial for their complementation and supplementation with other compounds and improve food production more sustainably.
